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R. I. WRIGHT. MOTOR CONTROL SYSTEM.

- APPLICATION FILED APR 9| 1920 RGISSllGd May 18, 1920.

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R. WRIGHT. MOTOR CONTROL SYSTEM.

APPLICATION FILED APR. 9, 1920.

Reissued May 18, 1920. 114,86 1

2 SHEETS-SHEET 2.

Witness. .6

7? PM IDS/6731?)? E 1 v M T 1 i M BEUBENI. WRIGHT, or wIcKLIFFE-oN-rHE-LAKE, onro, ASSIGNOR To THE nnnornro CONTROLLER & MANUFACTURING COM Tron 01 euro. 7

IPANY, F CLEVELAND, OHIO, A CORPORA- moroaconrnon sYs'rEM.

Specification of Reissue d Letters .Patent. fleig gflfl May 18 1920 ori inal No. 1,274,489, dated August- 6, 1918, Serial No. 162,891,. filed A ril is, an; Application for reissue filed April 9, 192%). Serial No. 372,685.

To all whom it may concern Be it known that I, REUBEN I. WRIGHT,

a citizen of the United States, residing at Wickliffe-on-the-Lake, in the county. of Cuyahoga and State of Ohio, have invented new and useful Improvements in Motor- Control Systems, of which the following is 1 a s ecification.

hlS invention relates to motor control.

\ When two or more motors (particularly .series motors) which are mechanically connected to the sameloadand electrically con- 'nected in parallel are quickly reversed by reversing their line connections while the i v motors are running, or stopped by dynamic braking, it frequently occurs that large, dangerous or destructive circulating currents set up in the local circuits-"of the associated motors.

' able electro-magnetic and the physical inequalities of the several motors employed,

and various attempts have been made to overcome the undesirable effects of these in equalities by specially designing the motor control systems.

Heretofore, control systems designed to obviate these circulating currents which occur on rapid reversal or dynamic braking have introduced other disadvantages. I For instance, one type of such system, using series motors, segregates the fields of the motors from their arallel connected armatures; this type e ectually eradicates or satinconvenience, and uncoordinated operation 1 of the several motors. r

- In my improved motor control system, j

. wound contactors for 'short-circuitin the advantages of using a separate controller for each motor are obtained without the disadvanta s above mentioned.

'braking','- I divide up th e resistance of the accelerating rheostat among the motors and i [connect it to them in such manner that, if

This is due to theunavoidthe circulating current tends to set up, it "will be limited by. the resistance to a safe amount. .In each motor, of which any numthe divided rheosta't resistance of all the motors is controlled by. a single set of y and the same resistance and switches may be used both foraccelerating and for'dynam ic braking.

switches In the draf i'ir'gs, Figurel s hbwsa motor control systen'f "'e"mbodyin,g my .invention when applied to three series motors arranged to be accelerated in one direction,

rapidly reversed and accelerated in the other direction. Fig. 2 is a simplified diagram showing a form of my invention similar to Fig. 1; Fig. 3, a diagram also in siniplified form, but showingmy invention ap f plied to three series motors arranged to be accelerated and then! braking; Fig. 4, a simplified diagramsimilar to Fig. 3, but employing only two banks of resistance; Fig. 5, a simplified diagram showing four reversing motors with dynamic braking connections for two of them;

and Fig. 6, a diagram similar to Fig. 5, but employing only three banks of resistance. Referring to Fig. 1, I have shown at A,

A A the motor armatures, at F F, F

their series fields. The armatures A A, A are mechanically connected to the same load, as indicated in the diagram. R to R stopped by dynamic inclusive are sections ofstarting resistance. 7

SF, SF SR, SR are shunt wound reversing switches, the, switches SF and SF closing together to give current to the motor armatures in one direction. to drive them forward, and the switches SR SR closin together after the switches SF and S 1 have been opened to give current to the motor armatures in the reverse direction to drive them backward. S}, S, S are shunt 1 the sections of resistance R to ,R to 'acce erate the motors. L is a shunt wound main line switch. At'M is shown a master controller, preferably manually oggrated. By manipuating the master arm 2 ofthe master controller, the various operations of the-system may be controlled at will.

The "lloclc-open relays L L Ofi LQ are series wound, that is, their windings are energized by motor current. Each of these switches has the peculiar characteristic of;

remaining in its normal, or open, position whenthe current in its windin is above a predetermined value, and of c osmg when the current 1s below, or is lowered to a point below, the predetermined value. An

'- may be u sed,-but I prefer to use that form shown in Canfields application, -Ser1al.

suitable form of such lock-open switc closing the contactor S master arm, the contact 28,-the wire 29, the

to close, and closes. If now the master arm be moved to the position f, the control current will flow from the negative-supply Wire 1 on the master controller, through the contacts of the relay L0 the wire 30, the

coil 52 of the-contactor S and the wire 31 to the positive supply wire 5, energizing and When the contactor'S closes, it short-circuits on its contacts the resistance sections R R R, that is, one section in the circuituof each motor.

The shor't-circuiting of the section R causes my invention as shown,

With the master handle M in the position w the coil 4 of the line switch L, to the posi.-' 'tive' supply wire 5, closing the switch L. Current also flows from the negative on thev shown, allthe switches are in their normal,

or open, positions shown, their windings be 'ing deenergized. To start and accelerate the motors in the forward direction, the master arm is moved to the position f Control current'then flows fro'm'the negative supply wire l on the master. controller, through the master arm, the contact'2, the wire 3, and

master controller to the contact 6, and thence by positive supply main 10', energizing and closed, main current flows from the positive the current in the wire 26 to flow through the mild the relayv LO the wire 32, the

contacts of the contactor the wire 33', the

coil of the relay L0 and the resistance sections R, R to the negative main27. The

peak of current resulting from the short-' circuiting of the resistance section B is suffficient to lock open the relay L0 When the current falls to the value for which the relay L0 is set to close, it closes, and, if the master arm be now moved to the positionf, current will flow from the negative on the master controller through the master arm, the contact 34, the Wi're35, the contacts of the relay L0 the Wire 36, thecoil 53 of a the contactor S and the wire 31 to the posithe wire], and the coils 8 and 9 .of the forward switches SFand SF, to the[ a section of resistance in each motor circuit, t closing the forward reversing switches.

When the 'switchesL, 'SF,'.and.;SF have supply main 10 to the point 11, where it divides, taking. three separate paths,-by .way .ofthe wires 12, 13, and 14, the contacts of the switch SF, and the wires .15, 16, and-17,

to the motor armatures A "A A, respectivel and thence by the wires 18, 1'9, and

-' 20, t e contactsof the switch SF and the wires 21, 22,28 to the fields F F F.-

From the field'F the current flows by the vwire 24, the, resistance section's R", Rfifan'd RLandthe contactsof the switch L to the negative ,supfply main 27 from the field F? ows by-the wire25, the resist L0 is set, it closes, and,

tive wire 5,,closing*the contactor S and ance sections R fRt, R, and the contacts of the switch L to thene'gative; and from'the field F the current flowsby the wire-26, the

coil of the lock-open relay -LO ,'-the'resistance-sections'R R,*and R, and: the contacts of The motors are thus en'er zed,.the

the switch L to .thenegative supply main2 7.

tive wire 5. The current in this circuit energizes and closes the contactor S and, as in the case of the contactor S short-circuits resistance section R, R Rt. Whenthe current fallsto the 'value for which the relay I ifthe master arm be moved to the position 7, the current will flow from thecontact37, the wire 38, the contacts of the relay LO, the wire 39, and lathe coilf54 of the contactor S to the posishort-circuiting the resistance sections R R, R". *The resistance is now all cut out,

ward direction. 7

By; moving the 'master arm point by point, as above described, the time of the closure of the contactors S S S? may be delayed at will." By moving the master arm at once to the full-on position f, the con- "tactors S 8 S willclose in succession, under the automatic currentdimit control of v the lock-open-relays LO, L0, L()*, and f turea'nd the series field o ,each being ,in series with three sections of starting resist ance across the supply-mains. The current which first {flows through. the' motor armature A", the field Fflthe wire 26, and1the automatically bring the motors up to speed. By moving" the. 1 master arm; backwardtoward the off position, any one or all of the l 'contactors S, S, S may be opened, rein Q coil of the relay LOlocksIthatrelay open.

As the motor accelerate s, the current falls to the value fo r which the relay LO set serting'the speed of the motors. I

- With themotors running in the'forw'ard I direction, as above described," if it be de and the motors run at full speed in the forresistance sections to reduce the" which is lockedopenby the sired quickly to reverse their direction, the master arm is first moved'to the off POSI- tion shownin thedrawing, whereupon all of the shunt-wound switches and contactors open, denergizing the motors and opening the lock-open relays. The master arm is then moved, intothe position f. Control current will now flow from the negative wire 1 on the master controller, through the master arm, the contact 40, the wires and 3, and the coil 4 of the switch L to the-positive supply wire 5, closing the switch L, as

before. Current will also flow through the master arm, the-contact 41, the wire 46, and the coils 47 and 48 of the backward revers-.

ing switches SR and SR to the positive supply main 10, 'closin the reversing switches 'SR and SR. M tor current will now flow to -'the-motors from the positive supply main 10, dividing into three paths at 11 and flowing by 'way of the wires'49,

. 50, 51," thecontacts of the reersing switch SR the wires 18. 19 20, the motor armatures A A A, thewires 15 16, 17, the coutacts-of the switch SR, the wires 21, 22, 23, the series fieldsF F F the wires 24. 25', and 26, the coil of the lock-open relay L0 the resistance sections R to R". and the con- ,tacts of the switch L to the negative supply main 27.] The current flows through the fields in the same direction as before, but in the reverse direction through the armatures. The armatures, therefore, slow down in the forward direction and stop and then begin to rotate in the reverse direction. During this reversal, there is a tendency for local current to flow from 'one motor to another, but in my improved control system herein described, by the placing of a portion of the starting resistance directly in series with each of the motors, this circulating current, if it tends to flow, will be reduced to a safe amount by the resistance,

for example, the path of such a circulating current between the armatures A and A would be from the armature A through the wire-19, the middle contacts of the switch SR the wires oO-and- 4 9, the lower contacts of the switch SR the armature A the wire 15, the-lower contacts of the switch SR, the wire 21, the field F the wire 24, there sistance sections R R", R", the lowercontacts of the switch L, the wire 27, the mid-- dle contacts of the .s'witch'L, the resistance sections R R", R ,.the wire 25, the field F the wire 22, the middle. contacts of the switch SR, and the wire 16 back to the armature A ,'-'.,but this circulating current would be'redliced to a safe amount by the resistances Rfi-R, R", R R R in series. Circulating'currents between any othertwo of the motors would likewise be made safe.

When the motorshave come to rest and have started to rotate in the opposite, or

backward, direction, the accelerating con- 'tions and "accelerate the motors.

tactors S S 8*, close automatically in suc-.

cession, upon the automatic closure of the lock-open relays L0 L0 L0", or, close vsuccessively upon the movement'of the master arm successively into positions f, f, f". It will-be noted that one set of accelerat-' ing contactors, S S S is employed to control simultaneously resistance sections for all of the motors; that the armature and series field of, each individual motor are in .pureseries relation with eachother, so that one shown in solid lines and the other in dotted lines for forward and for backward running. it is understood that all the switch elements having the same reference characters are parts of one switchandoccupy thesame positions at the same time. To start the motors in the forward direction, the. switches 'R and RR are first moved to the solid line positions, and then the switches L are closed. Current then flows from the positive main 10 to the negai 1e tive main 27- through three similar para circuits, each containing an armature, a field, and three resistance sections in series.

The contactors S L- S are then successively closed to cut out the resistance sec- To stop andreverse the motors, all the switches are -first opened, and then the switches and are moved to their dotted line POSltlOIlS RR and the switches L are closed. The circuits thus established are the same as before, ex-

cept that the current flows in the opposite direction through the armatures A, A, A

These changes of the switches stop the .motors and start them in the op osite direc-' tion. The contactors S, S v 3 are again successively closed to accelerate the motors.

If desired the switches L /may be omitted.

In this case, the motor current beinginterrupted by opening the reversing switches R and RR, the resistance sections R, R and R? would be connected directly to the negative main 27,

In'the simplified diagram shown in Fig. 3, I have illustrated my invention applied 1 to the purpose ofpreventing circulating currents between any two hoisting motors when they are stopped by"-dynamic'braking. The motors are electrlcallyo driven while hoisting a load, but during a lowering operation the-motor is meclianicallyl' reversed bythe load. As in Fig. 2,"all switch elements bearing the same reference characters are parts of one switch and occupy the same positions at the same time, To

start andaccelerate themotdrs, the switches B and the contactors S S and S? are opened, and the switches L and L are closed. Motor current then flows fromthe positivemain 10 to'the negative main 27 through three similar parallel circuits, each containing a motor-armature, a series field,

' and three sections of resistance in series.

braking circuit consisting of anarl'natur'e, its series field, and three sections of res st-L The contactors 1, 8 S? are then succes sively closed to short-circuit the resistance sections, whereby the motors are-brought up to full speed. namic braking during the lowering of the load, the switches L, L, the contactors S S S are first o enedand then the switches B are closed. his gives a dynamic braking circuit for each motor electrically isolated fromthat of each other motor, each ance in series. The braking current of the armature A ,for example, flows from the armature; A through the series field F and theresistance sections R R, R, the

. l the negative main 2 wire 50, and the switch B back to the motor armatureA The dynamic braking circuit for each of'the othertwo motors is similar. As the motors slow down, the contactors S S S areclosed successively, cutting'outthe resistance sections to maintain the braking efl'ect. When the motors have finally stopped, they may be started again by opening the contactorss S S to reinsert the starting resistance, and opening the switches B and closing the switches L and L If desired the switches L may be omitted, the current supply being broken on the switches L and the resistance sections R, R and R being connected,

In the "form of my inventionv shown on Fig. 4,'-thr eehoisting motors and two banks 7 of] resistance'fsections are employed, one bankbonsistin'g ofthe sections R R, R, and the other of the sections R R R,. All

' threeof the mechanically connected motors are energized for acceleration, but onl two are u'sed for dynamic braking. All switches bearing the same reference characters are parts of the same switch, and foccupythe same positions at the same time. To start the motors, the contacts-S S S and B are opened and the switches L and L are closed. Current then flows from the positive main 10 to the negative main v27 1 through: the three motorsand their fields in parallel, and then through 'the two resistance ,banks in parallelLj-L The accelerating contactors S S S areclosed successively,

cutting out the resistance sections whereby 0 stop the motors by (1y v directly to the ,motors are brought up to 'full speed. Eachcontactor cuts out two sections simultaneously; for example, the, "contactor S ;cuts out the sections R and R ,To stop the the contactors S 8*, S are opened, and the switches Bare closed. This segregates the middle motor and its field from the other motors, each of which has an isolated dy Ila-micbraking'circuit comprising its armature,.its series field, and one of theresistmotors by dynamic brakin during ,the low ering of the'load, the switches Land L ance banks in series therewith. 1 The contactors are closed successively, to 'cut out the resistanceand maintain the braking effect.

The switches K may be employed and" when open-wi1l segregate the middlef'motor from the others, for dynamic brakingp-ih which; case the switches L may be omitted, and-the resistancesections R and-.R connected directly to the negative main 27: In both Fig. 3 and Fig. 4 dynamic braking current is produced v by the load overhauling the I ing, and reversing switches being unnecessar Fig. 5, four: motors ,with' reversin'g connecmotors, current, passing through the armature'in the samedirection as during hoists n the form of my invention shown .in

tions are employed with'a bank of resist- I ,z'

yance for each motor, and' with dynamicps' braking connections for, two motors. -To. start the motors, the switches B and the con- 'tactors S S S are opened and the;

switches L are closed, and the reversing switches-R and are closed to the solid line positions, for example. As the motors sively tocut out the resistance-sections to bring the motors up to speed, eachcontac tor .cutting out four sections of resistance simultaneously, one from each bank; as, for example, the contactor S cuts outlthe secstart, thecontactors S S, S close succestions R R R and R To reverse the motors, the contactors S S, S. are opened,

and the switches R and RR are moved to;

' the dotted-line positions, the motor armaa tures then receiving current in the opposite direction, which stops them and then starts them in the other; direction.

The contactors S S 3*; are then closed successively to accelerate the motors in the other direc- 'tion. To stop the'motors by dynamic braking, the switches 'L' and the contactors S S and S Lare opened, andithe switches'B are closed and the switches R and RR are thrown to the reverse or" dotted-line position, thus giving for each'of the two out-'- side motors an isolated dynamic braking c rcuit lncludlng an armature, a series field,

and a resistance bank in series therewith.

The contactors arethen closed successively to' cut out the resistance to braking efi'ect. 1.

maintain the 14,sei

In theform of my invention shown in resistance and dynamic braking connections for two of the motors. The operation is as follows: To start the motors in one direction, the switches B and the contacts 8, S, S are opened, and the switches L and L are closed, and the reversing switches R and RR are closed in the solid-line positions, for example. The current to the motor armature A flows through the armature, the series iield'F and the resistance sections R, R, R in' series therewith. the switches N and N being closed. The motorshaving' armaturcs A. A, A, and the series fields F. F. F arein parallel, and the current flowing through them divides between two resistance banks consisting respectively of the resistance sections R, R, R lv", ll. \Vhen the motors start, the contacts S, S, S are closed successively to accelerate the motors. To stop themotors and start them in the other direction, the reversing switches are moved to the dottedline positions, giving current in the opposite direction to the motor arn1atures'.- The coutactors S, S, S are then closed succcssively to accelerate the motors in the other direction. To stop the motors by dynamic braking, the switches L or L and L, and the switches N and N are opened, and the switches B are closed. and the reversing, switches li and RR are thrown to the reverse or dotted-line position, thus giving for each of the twooutside motors an isolated'dynamic braking circuit including an armatore, a series field, and a resistance bank in series therewith. The contactors are then closedsuccessively to cut out the resistance to maintain the braking eifect. If desired, the switches'L may be omitted; or by employing the two switches N andN and the switches L, the switches L may be omitted. When the switches L are omitted. the re rersing switches RR are connected directly to the positive main 10, and when the switches L are'omitted the resistance sections R, R", R" are connected directly to the negative main27.

In these diagrams it will be seen that one set of contactors S S", S controls the starting and braking resistances for all of the motors; that the armature andseries field of each individual motor are in series relation in each motor to pro erly distributethe load; that the dynamic raking circuit for and R each motor is segregated electrically from those of the others, so that localcirculating currents which otherwise would-tend to 00- cur when the dynamic braking circuits are established, are entirely obviated; that during the period of stopping and reversing the motors, local circulating currents between relays any two motors flow through two banks of resistance sections in series, and are thus reduced to a safe amount; and that a coinplete rheostat for each motor is not essential 511108, as shown,there may be fewer rheothe switches 5 S S -controlled only bythe contact points, such as f, on the master M. hlymvcntion is not limited in its application to the systems of. connections illustrated, since other arrangements, modihcations, and combinations of the various essential features of my invention may be made .without departing from its spirit.

I claim: 7

1. In a motor control system, current sup,- ply mains, a plurality 'of'motors arranged in parallel and having their rotary elements mechanically connected so as to rotate together, meansconnecting the field and armature of each motor in series for each direction of rotation of the motor, a plurality of banks of resistance sections for the motors,

means for establishing dynamic braking cir-.-

cuits for some of the motors, a switch for cutting out simultaneously a resistance section from each bank to start the motors and vmeans for causing the said switch to cutout simultaneously a resistance section from each bank in each dynamic braking circuit, each resistance bank being connected across the supply-mains and in series with some of the motors.

2. In a motorcontrol system, current supply mains, a plurality of motors arranged in parallel and having their rotary elements mechanically connected so as 'to'rotate together, reversing switches arranged to connect the armature and field of each motor inseries for each direction of rotation of the motor, a plurality of banks of starting resistance sections, each section being connected across the supply mains and in series with some of the motors, and means wherei 1 may be applied to' trical path from onemotor to another will be in series with two banks of resistance sections.

3. In a motor control system, current sup ply mains, a plurality of series motors arranged in-parallel and having their rotary elements mechanically connected so as to ro- "tate together, reversing switches arranged to connect the armature and field of each motor in series for each direction of rotation of the motor, a plurality of banks of starting resistance sections, each section being connected across the supply mainsand in series with some of the motorsyan accelerating switch for cutting but simultaneously a resistance section from each bank to start the motors, means for opening theranged to connect the armature and field of each motor in series for each directionof rotationof the motor, a plurality of banks of starting resistance sections, each section being connected across the supply mains and in series with some of the motors, a dynamic braking circuit for one of the motors inbraking, and means whereby, when the dynamic braking Jcircuit for said motor is closed, the current flowing in said motor is prevented from flowing in another motor.

6. In a 'motorcontrol system, current supply mains, a plurality of series motors arranged in parallel and having their rotary elements mechanically connected so as to rotate together, reversing switches arranged to connect the armature and field of each motor in series for each direction of rotation of the motor, a plurality of banks of starting resistance sections, each section being connected across the supply mains and in series with some of the motors, a dynamic braking circuit for one of the motors including one of the banksof resistance sections, and means whereby, when the reversing switches operate .to reverse the-motors, or when the dynamic braking circuit is closed, current 'above a safe value is prevented from flowing from any motor to any I other motor.

g 7. In a motor control system, current supply mains, a plurality of series motors arranged in parallel and having their rotary 'elements mechanically connected so as to eluding one of the banks of resistance sections, and means whereby, when the dynamic braking circuit for said motor is closed, the current flowing in said motor is prevented from flowing in another motor.

5. In a motorcontrol system, current supply mains, a plurality of series motors arranged in parallel and having their rotary elements mechanically connected so as to rotateitogether, reversing switches arranged to connect the armature and field of each motor in series for each direction of rotation of the motor, a plurality of banks of starting resistance sections, each section being connected across the supply mains and in series with some of the motors',-'a dynamic braking circuit for one of the motors including one of-the banks of resistance sec-t tions means for establishing said dynamic braking circuit, a switch for cutting out simultaneousl'y-a resistance section from each rotate together, reversing, switches arranged to connect the armature and field of each motor in series for each direction of. rotation of the motor, a plurality of banks of starting resistance sections, each section being connected acrossthesupply mains and in series with some of the motors, a dynamic braking circuit for one of the motors in cluding one of the anksof resistance sections, a switch for cutting out simultaneously a resistance section from each bank to' start the motorsand for subsequently cutting out a section from one of the banks to stop one of the motors, by. dynamic braking, means for opening the accelerating switch to reinsert the starting resistancesections. before the reversing switches may be operatedto reverse the motors and before the dynamic braking circuit may be closed, and means whereby, when the reversing switches oper- .ateto reverse the-motors,or the dynamic braking circuit is closed, current above a safe value is prevented from flowing from p an motorto any bank to start the motorsand ,for'subse-' 1 quently cutting out a from one of the banks to stop-one or the motors by dynamic,

other motor;

1-gned at Cleveland, Ohio, this 30th day of arch, A. 1920.

1. v REUBEN I. WRIGHT, 

